Cisco Nexus 9000 Series Configuration Manual page 118

Configuring Congestion Avoidance
Command or Action
Step 5 hardware qos q-noise percent value
Cisco Nexus 9000 Series NX-OS Quality of Service Configuration Guide, Release 7.x
104
Purpose
Value Network Forwarding
of Engine (NFE) enabled
alpha switches
Definition Max % per
queue
1 1/64 ~1.5%
2 1/32 ~3%
3 1/16 ~6%
4 1/8 ~11%
5 1/4 20%
6 1/2 ~33%
7 1 50%
8 2 ~66%
9 4 ~80%
10 8 ~89%
For example, if you configure a dynamic queue size of 6, then the alpha
value is ½. If you configure a dynamic queue size of 7, then the alpha value
is 1.
To calculate the queue-limit consider the following:
queue-limit = (alpha/(1 + alpha)) x total buffers
For example, if you configure a queue-limit with a dynamic queue size of
7, then the queue-limit can grow up to (1/(1+1)) x total buffers. This means
that queue-limit = ½ x total buffers.
Although the above calculations determine the maximum queue
Note
occupancy, the maximum queue occupancy is limited to 64K cells
in all cases for Application Spine Engine (ASE2, ASE3) and Leaf
Spine Engine (LSE) enabled switches.
Note Setting the threshold on ALE enabled devices is only supported for
the system level. It is not supported for the port level.
Tunes the random noise parameter. The default value is 20 percent.
Configuring Queuing and Scheduling
Leaf Spine Engine (LSE) enabled switches
Definition Max % per ASIC value
queue
1/4 ~20% 1
1/2 ~33% 3
3/4 ~42% 5
1 1/8 ~53% 8
1 3/4 ~64% 14
3 ~75% 16
5 ~83% 18
8 ~89% 21
14 ~92.5 27
18 ~95% 31